Flexible vinyl sheet, film, and flexible vinyl coated fabric (hereinafter referred to as "vinyl products(s)") are very versatile materials and find a wide variety of applications. Curtains for windows and showers, coverings for home and office furniture, automotive seat covers, single ply flexible vinyl membranes for covering industrial roofs, wall coverings, shoe uppers, purses and agricultural sheet illustrate the diversity of uses for this material.
Despite its wide utility there are some problems associated with the use of flexible vinyl in many applications. One of the more serious problems involves cracks or tears that develop in flexible vinyl products after they have been exposed to heat and or sunlight for several years. These cracks and tears generally mark the end of the useful life of the vinyl. In addition to cracking and tearing, flexible vinyl products frequently exposed to moisture and high humidity such as flexible vinyl roofing membranes are susceptible to becoming covered with biological growth.
Already manufactured flexible vinyl products can develop cracks and tears or become covered with biological growth because the original manufacturer elected not to include the costly additives needed to prevent these problems. For example, it is known in the art that special function additives such as UV stabilizers, mildewcides, vinyl heat stabilizers, and the like can be incorporated in the vinyl plastic at the time when the vinyl plastic compound is being manufactured. Conditions which must be met in order to incorporate special function additives in vinyl products at the time of manufacture according to the Plastics Engineering Handbook include heating the loose mixture of vinyl resin and additives of 300.degree. F. to 350.degree. F. temperatures in order to fuse the vinyl dispersion, use of high shear, low speed mixing to disperse the resin in the plasticizer, and use of special very fine particle size, high porosity resins known as dispersion grade resins. But it is also known that such special function additives cannot be incorporated in vinyl products after they have already been manufactured and fabricated. Some additives are heat sensitive and would decompose if added during the manufacture of flexible vinyl products.
A need exists for a method for introducing useful additives into already manufactured and fabricated flexible vinyl products. U.S. Pat. No. 4,284,444 attempts to respond to this need by disclosing a method for imparting to already manufactured and fabricated polymer films and fabrics antibacterial, electrical conductivity enhancing, antistatic, animal repellent, antifungal, and insecticidal properties by applying to the surface of the product selected activating agents. The activating agents have the ability to migrate by themselves unassisted into the body of the already manufactured and fabricated polymer product to impart an effective level of activity. Although this method has proven useful it is not without its disadvantages. For example, when certain U.S. Pat. No. 4,284,444 activating agents are applied to the surface of a flexible vinyl product they have proven to be ineffective according to the information provided in U.S. Pat. No. 2,284,444. It is reported in U.S. Pat. No. 4,284,444 in example 85 (Table 4) that tributyl tin acetate was not an effective activating agent in the process of the U.S. Pat. No. 4,284,444 invention as evident from the fact that the tributyl tin acetate underperformed (it did not provide effective activity) the control (example 77). However, example 5 of the present application shows that tributyl tin acetate is effective when applied by the process of the present invention.
The activating agents of U.S. Pat. No. 2,284,444 may be applied to the polymeric product as a component of a polyvinyl chloride plastisol, as a solution in a volatile, non permanent carrier liquid containing a binder resin, or the activating agents may be applied neat. It is a disadvantage to have to apply U.S. Pat. No. 4,284,444 activating agents to a polymeric product as part of a vinyl plastisol because vinyl plastisols must be fused at elevated temperatures after application in order to perform their function.
It is frequently not possible to heat already manufactured and fabricated vinyl products such as a vinyl fabric covered chair or an automobile with a vinyl roof to elevated temperatures without damaging other portions of the product. The volatile solvent method of introducing activating agents also has its disadvantages. In addition to the potential for damage to the polymeric substrate from attack by the volatile solvent, this method for applying U.S. Pat. No. 4,284,444 activating agents suffers from the disadvantage that polymeric products so treated are left coated with a binder resin that is not necessarily desired. The number of activating agents which when applied neat to a polymeric product will then migrate into that product at economically significant rates is extremely small.